Heat-extrusion method

ABSTRACT

A method and machine for the manufacture of metallic parts by heat extrusion of a heated metal billet through a draw-plate. Prior to being pressed, by means of a chisel the front surface of which is smaller than that of the billet, the latter is coated on its lateral surface, as well as on its front face, with a powdered retaining product, so that after extrusion there remains on the inner wall of the bore of the container housing the billet a skirt of metal whereby is produced a metallic part the outer surface of which is devoid of any defects.

United states Patent [191v Feb. 12, 1974 Creuzet HEAT-EXTRUSION METHOD [76] Inventor: Robert Creuzet, Route de Beyssac,

' 47 Marmande, France [22] Filed: Feb. 9, 1971 [21] Appl. No.: 113,820

[30] Foreign Application Priority Data Feb. 19, 1970 France 7005988 [52] US. Cl. 72/46, 72/258 [51] Int. Cl. B2lb 45/00 [58] Field of Search..... 72/273, 266, 264, 255, 258,

[56] References Cited UNITED STATES PATENTS 2,773,593 12/1956 Schmollinger 72/46 3,434,323 3/1969 Ormerod 72/258 3,184,945 5/1965 Hornak 72/258 X 1,128,058 2/1915 Schoop 117/105 3/1915 Schoop 117/105 2/1915 Schoop 117/105 ABSTRACT A method and machine for the manufacture of metallic parts by heat extrusion of a. heated metal billet through a draw-plate. Prior to being pressed, by means of a chisel the front surface of which is smaller than that of the billet, the latter is coated on its lateral surface, as well as on its front face, with a powdered retaining product, so that after extrusion there remains on the inner wall of the bore of the container housing the billet a skirt of metal wherebyis produced a metallic part the outer surface of which is devoid of any defects.

1 Claim, 3 Drawing Figures 1 HEAT-EXTRUSION METHOD FIELD OF THE INVENTION The object of the invention is a method for heatextrusion of a metal, as well as a machine to carry out this method.

PRIOR ART Methods are known which yield heat drawn metal pieces, by extrusion, by means of a ramming part or chisel, of a heated billet set in a holder.

The use of these methods raises difficult problems, owing to the high temperatures, to the abrasion phenomena, and also to the impurities which are present at the periphery of the billet, especially owing to oxydation.

It has been suggested to facilitate drawing by extrusion by using a lubricant, usually interposed between the billet and the bore of the holder. The lubricants which are used are frequently glass ba'sed lubricants. It is then necessary to subject the parts obtained by extrusion to a scouring operation.

SUMMARY OF THE INVENTION On the contrary it is suggested, in the method according to the invention, to retain on the inner side of the bore athin layer of the billet of metal to be extruded. The extruded part thus obtained then presents, directly after extrusion, all the qualities required, without it being necessary to subject it to further processing.

According to the invention, a retaining product is present between the billet and the inner surface of the bore housing the billet, and the diameter of the ramming side of the chisel is slightly smaller than that of the bore. i

It has been found that, under those conditions, for steel as well as for metalsknown tobe difficult to extrude, such as titanium, the flowing capacity of the metal of the billet heated to the extrusion temperature is sufficient for the greater part of the bulk of the billet to part from the outer layer and to be extruded through the draw-plate, a thin layer or skirt remaining on the inner surface of the bore, retained by the interposed product.

This skirt may afterwards be easily removed.

The invention also provides to interpose the retaining product between the front side of the billet and the plate through which the metal is to be extruded, the

forward stroke of the piston or similar carrying the chisel then being restricted so that there remains, after extrusion, a disc of the metal of the billet which forms, together with the skirt, a residual heel.

The piece obtained by extrusion is devoid of surface defects. It may be thin or present, in the case of a shaped piece, parts thinner than those which could be obtained with the known methods.

The following description, made by way of example, refers to the appended drawing, wherein FIG. 1 is a very diagrammatic sectionnal view of a part of a machine according to the invention FIG. 2 is similar to FIG. 1, for another condition FIG. 3 relates to another condition.

The apparatus includes a holder 10, which may be mounted so that it may be displaced to allow the insertion of a billet ll of themetal to be extruded.

In a modification, the piston 12 provided for the extrusion is removed at a distance sufficiently large from the holder so that the billet may be inserted.

This latter is at a temperature suitable for extrusion, of about 1,300 for steel, and is covered, for instance by the Schoop process, with powdered alumina, or another refractory oxide, such as zirconia, before it is inserted in the holder 10. The Schoop process referred to herein is a technique in which a spraying is performed by means of a device known as a Schoop gun. The material to be sprayed is brought to a high temperature by means of an internal arc and then is sprayed under pressure. The spray material thus sticks onto the sprayed surface, which in the present case, is the surface of the billet. The process results in a coating of microdrops on the sprayed surface. In the case of Zirconia, the type of blow pipe employed is a plasma blow pipe.

The piston proper 12 is followed by a pressing chisel 13, which may easily be replaced when necessary, and the diameter of the front side 14 of the chisel 13 is very slightly smaller than the diameter of the facing end side 15 of the billet 11' which is appreciably equal to that of the cylindrical chamber 16 of the holder 10. In the figures, for the sake of clarity, the difference between the diameters of the chisel and of the billet is somewhat exaggerated, and the clearance between the cylindrical chamber and the billet, which in practice is of about 2 to 3 mm., is likewise exaggerated.

Alumina or the like covers not only the lateral side 17 of the billet, but also the hind side 15 and also the is extruded through the draw-plate 19, goes through the drawing aperture 20, and the shaped piece 22 projects at a high speed beyond the bed 21, going through its aperture 23. The piston 12 goes on until its front side 14 is at a comparatively small distance, ranging about one or several centimetres, from the forward end side 24 of the draw-plate 19.

There remains, inside the holder 10, a heel 25 (FIG. 2), which includes a bottom 26, the thickness of which is equal to the distance between the forward end side 14 of the chisel 13, in its foremost position, and the side 24 of the drawing-plate, and a lateral wall 27 making up a cylindrical sleeve or skirt, the thickness of which isequal to half the difference between the diameter of the front side 14 of the chisel and the diameter of the outer surface of the billet 11, that is about 10/10 to 15/10 mm.

To remove the heel 25, the holder 10 is moved away from the draw-plate 31 (FIG. 3) which abutts against the counter draw-plate 32 and this latter against the bed 33, and the shaped piece is cut off at a short distance from the front side 34 of the holder. This latter, together with the chisel 35 and the piston 36, being moved away from the draw-plate, a forward movement of the piston 36 and of the chisel35 expels the heel 25.

A new billet, covered with the retaining product, is set into place in the housing 37 of the holder, and the holder together with the piston and it's chisel is brought back to the condition shown in FIG. 1 from this condition, the forward motion of the chisel extrudes the new billet, which yields again a drawn piece the section of which corresponds to that of the draw-plate.

The alumina or the like interposed between the lateral surface 17 of the billet and the inner wall of the chamber 16 of the holder 10 has the effect of retaining the skin of the billet on said inner surface, the internal plasticity of the metal of the heated billet being sufficient for this metal to flow through the draw-plate and for the extruded metal to slide with respect to the outer part, which adheres, through the interposition of the powdered alumina, to the inner surface of the chamber 16, thus leaving the annular sleeve 27 of the heel.

The shaped piece 22 which is obtained is purely metallic, that is its surface does not include a non-metallic coating. It may be used as it is, after being cooled down as usual.

In case of need, a simple fininishing operation yields a high surface quality, if so required.

The method allows one to obtain shaped pieces with very thin parts, for instance with edges of about 2/10 mm., directly after being drawn.

The invention applies to the extrusion of steel, titanium, and other metals.

What I claim is:

l. A process for manufacturing a metallic member from a hard class of metal such as steel, titanium and the like by means of high temperature extrusion of a hard metallic billet located in the bore of a container through a die under the effect of a dummy block whose front surface is smaller than tat of the facing billet, wherein a powder of a refractory oxide selected from the group consisting of alumina and airconia i s Schoop coated onto the peripheral lateral surface and the front and rear faces of the billet before it is placed into the bore of the container at a temperature in the range of l,300. 

1. A process for manufacturing a metallic member from a hard class of metal such as steel, titanium and the like by means of high temperature extrusion of a hard metallic billet located in the bore of a container through a die under the effect of a dummy block whose front surface is smaller than tat of the facing billet, wherein a powder of a refractory oxide selected from the group consisting of alumina and zirconia is Schoop coated onto the peripheral lateral surfaces and the front and rear faces of the billet before it is placed into the bore of the container at a temperature in the range of 1,300*. 